NOTE: Delete bending of medium or high pressure
pipe when not included in project.
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Use long radius ells where appropriate to reduce pressure drops. Pipe
bends in lieu of fittings may be used for piping where space permits. Pipe
bends shall have a uniform radius of at least five times the pipe diameter
and must be free from any appreciable flattening, wrinkling, or thinning of
the pipe. Mitering of pipe to form elbows, notching straight runs to form
full sized tees, or any similar construction shall not be used. Make
branch connections with welding tees, except factory made forged welding
branch outlets or nozzles having integral reinforcements conforming to ASME
B31.1 may be used.
a.
Bending of High Pressure Pipe: Prior to bending pipe for high
pressure systems, the Contractor shall submit for approval written
fabrication and inspection procedures and calculations showing the
required minimum wall thickness of pipe after bending. Only cold
bending shall be permitted. The fabrication procedure shall
indicate the required pipe wall thickness prior to bending,
equipment to be used, set up and bending procedures, and
inspection and acceptance criteria. Inspection shall include
verification of minimum wall thickness by ultrasonic or other
methods if deemed necessary by the Contracting Officer. No
wrinkles or other contour irregularities will be permitted in the
bent pipe. Check flattening in accordance with ASME B31.1.
Include required dimensional checks in inspection procedures and
acceptable values tabulated for each pipe size to be bent.
Qualified personnel shall perform nondestructive examinations
required in accordance with qualified procedures.
3.1.3.2
Clearances for Welding
Provide clearances from walls, ceilings, and floors to permit the
installation of joints. The clearances shall be at least 150 mm 6 inches
for pipe sizes 100 mm 4 inches and less, 250 mm 10 inches for pipe sizes
over 100 mm 4 inches, and sufficient in corners. However, the specified
clearances shall not waive requirements for welders to be qualified for the
positions to be welded.
3.1.3.3
Cleaning
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NOTE: Special cleaning requirements are mainly
intended for high pressure systems. Special
cleaning should also be considered for medium
pressure systems over 1724 kPa (gage) 250 psig which
may be subject to dieseling explosions when oil
contamination is present. Objective cleaning
standards are specified to simplify inspection and
acceptance in the field.
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Before jointing and erection of piping or tubing, thoroughly clean
interiors of pipe sections, tube, and components. In steel pipe, loosen
scale and other foreign matter by rapping sharply and expel by wire brush
and swab. Blow out both steel pipe and copper tube and components with
compressed air at 690 kPa (gage) 100 psig or more. Maintain cleanliness by
closure of pipe/tube openings with caps or plugs. Before making final
SECTION 15212N
Page 36
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